Western blot analysis.
Cells were lysed in Laemli buffer and run onto a 4%–12% SDS PAGE gradient gel. We used antibodies against p150CAF-1 ([16]; dilution 1/500), HP1α (2G9, Euromedex; 1/500), Histone H3 (Abcam; 1/500), H3K9me3 (Upstate; 1/500) and β-actin (Upstate; 1/40 000).